1. Field of the Invention
This invention relates to polyetherdiamines and, more particularly, this invention relates to novel curing compositions comprising aminated, alkoxylated derivatives of hydroxyalkyl-2-imidazolidones, prepared as described in copending application Ser. No. 07/928,582 incorporated herein by reference in its entirety. The hydroxyalkyl-2-imidazolidone initiator is reacted with an alkylene oxide and the resulting polyol subsequently undergoes reductive amination.
These novel polyetherdiamines, termed HEIMD-containing polyetheramines, exhibit improved elastomeric properties and can be used alone or combined with known polyoxyalkyleneamine curing agents and reacted with multifunctional epoxy resins to produce systems which possess a level of flexibility and toughness not usually achieved. Due to the unique structure of these amines, which contain cyclic urea, cured systems are more resistant to impact and are more extensible than are systems cured with blends of other polyetheramines of equivalent weight.
2. Related Art
It is known in the art that compounds with primary and secondary amine functions can be used as reactive hardeners in epoxy resin formulations employed for protective coatings, electrical embodiments, adhesives, etc. Many of the known polyethylenediamines have been used for such applications. Grayson et al., ed., Kirk-Othmer Encyclopedia of Chemical Technology, Third Edition, Vol 7, p. 593.
It is also known in the art that the utility of the polyethylenepolyamines as curing agents or hardeners for epoxy resin compositions can be extended through the use of numerous derivatives. For example, hydroxy-substituted amines can be prepared by the reaction of a pclyethylenepolyamine with ethylene oxide or propylene oxide. Cyancethylated polyethylenepolyamines represent another useful class cf derivatives.
Substituted imidazolines prepared by the condensation of polyethylenepolyamines with carboxylic acids or carboxylic acid derivatives have also been employed as epoxy curing agents. These curing agents are proposed for use in aqueous emulsion systems and to provide coatings with improved hydrolytic stability.
Polyethylenepolyamines can be condensed with di- and trifunctional fatty carboxylic acids obtained from the thermal polymerization of vegetable oil fatty acids to produce liquid, reactive polyamide resins. Various polyethylenepolyamines may be used in the preparation of polyamides, which may be characterized as low molecular weight, highly branched, highly viscous polymers with high amine functionality. The liquid polyamides often provide substantial improvements in flexibility of cured composites, leading to higher impact resistance and flexural strength.
Other derivatives of polyethylenepolyamines can be prepared by reaction with .alpha.,.beta.-unsaturated esters to reduce viscosities. Viscosity reduction can also be effected by blending the polyamides with the higher polyethylenepolyamines.
Other derivatives are prepared by reacting polyethylenepolyamines with an aliphatic, hydroxyl-containing carboxylic acid, with tall oil fatty acids and with keto-acids.
The products of polyethylenepolyamines and aromatic monoisocyanates, lower aliphatic aldehydes, epoxidized fatty nitriles and propylene sulfide are also useful as epoxy curing agents.
There is always a need in the field of epoxy curing agent for compounds which provide improvements in toughness (resistance to impact) and flexibility (elongation) of cured compositions, as measured by tests which are well-known in the art.
It would represent a substantial advance in the art if a curing agent were commercially available which had distinct, measurable improvements in strength properties, i.e., resistance to impact and elongation.
It would also be very useful in the art if such a curing agent could be used alone or blended with other curing agents in a predictable way to modify properties of cured systems.